Abstract

We investigate multiphoton states generated by high‐gain optical parametric amplification of a single injected photon,
polarization encoded as a “qubit”. Two different experimental configurations were adopted in order to investigate two different quantum processes: the optimal universal quantum cloning and the optimal phase‐covariant cloning. The output states of the two apparatuses were found to show the quantum superposition property of mesoscopic multi‐photon assemblies and the entanglement characteristics of the “Schroedinger Cat State”. This work represents an experimental attempt to test several fundamental quantum processes in a mesoscopic, or macroscopic frameworks. As it is well known, this is indeed one of the most challenging endavours of modern science.